1,382 research outputs found
Overview of ALICE results on azimuthal correlations using neutral- and heavy-meson triggers
The ALICE detector is dedicated to studying the properties of hot and dense
matter created in heavy-ion collisions. Among the probes used to investigate
these properties are high-momentum particles, which originate in
hard-scatterings occurring before the fireball creation. The fragments of hard
scatterings interact with the hot and dense matter and via this interaction
their spectra and azimuthal distributions are modified. This is probed by the
measurement of the nuclear modification factor, where the
spectra obtained in Pb-Pb collisions are compared to a pp baseline. A strong
suppression of charged hadrons as well as neutral- and heavy-flavor mesons was
observed at GeV/. Azimuthal correlations, using
high-momentum ( GeV/) hadrons as triggers, can provide
further insight into how the presence of the medium modifies the final
kinematic distributions of the particles. Comparison with theoretical models
can be used to test their predictions about the properties of the medium. We
give an overview of ALICE azimuthal-correlation measurements of neutral- and
heavy-flavor mesons with charged hadrons in pp collisions at TeV
and Pb-Pb collisions at TeV. We also present a
measurement of the correlation with jets in pp collisions at
TeV.Comment: Proceedings of '10th International Workshop on High-pT Physics at
RHIC/LHC era' conference, 9-12 September 2014, 9 pages, 7 figure
Experimental treatment of Quark and Gluon Jets
The separate study of quark and gluon jets is vital for the interpretation of
multiple variables behaviour observed in both high-energy hadron and heavy-ion
collisions in the present and future experiments. We propose a set of
jet-energy dependent cuts to be used to distinguish between quark and gluon
jets experimentally based on a Monte-Carlo study of their properties. Further,
we introduce the possibility to calibrate these cuts via gamma-jet and
multi-jet events, which represent clean production channels for quark and gluon
jets, respectively. The calibration can happen on real data and thus, reduces
the dependence of the method performance on Monte-Carlo model predictions.Comment: 5 pages, 3 figures, presented at the 6th Intenational High-pT at LHC
Workshop in Utrecht, 201
Study of particle production from quark and gluon jets in proton-proton collisions
We investigate whether and how different fragmentation properties of quarks
and gluons affect identified particle spectra. We present a systematic study of
, and production in minimum bias (inelastic, non-diffractive),
two- and three-jet events at RHIC, Tevatron and LHC energies. Through the study
of two- and three-jet events and various jet-production channels we can
directly access the fragmentation properties of quark and gluon jets. We
present MC estimate for the contribution of quark and gluon jets to individual
particle species spectra, that can be compared to experimental results and test
our current knowledge of the physics behind particle production inside jets.Comment: 5 pages, 3 figures, presented at Hot Quarks 201
Topological study of three-jet events in ALICE
The ALICE experiment at LHC is dedicated to study matter formed in heavy-ion
collisions, but also has a strong physics program for collisions. In these
collisions, protons will collide at energies never reached before under
laboratory conditions. At the high energies, ALICE will enable us to study jet
physics in detail, especially the production of multiple jet events, setting
the baseline for heavy-ion. Three-jet events allow us to examine the properties
of quark and gluon jets, providing a suitable tool for testing QCD
experimentally. We discuss the selection method and topology of three-jet
events in ALICE. The analysis was performed on two PYTHIA data sets, both
involving collisions at TeV with enhanced jet production.
The results from the dedicated jet MC production are discussed and compared to
previous studies at CDF and D\O. We investigate the possibilities to determine
gluon jet candidates.Comment: 9 pages, 5 figures, contribution to the "High-Pt Physics at LHC '09"
workshop in Pragu
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
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